Navigating uterine niche 360 degree: a narrative review

The increasing prevalence of cesarean section (CS) deliveries globally has sparked apprehension regarding potential long-term complications, notably the emergence of uterine niches. CS results in a scar that in certain patients, inadequate healing of that scar results in the development of a uterine niche. While most small niches show no symptoms, large cesarean scar niches in nonpregnant women can give rise to cesarean scar disorder syndrome. This syndrome is characterized by abnormal uterine bleeding, dysmenorrhea, and secondary infertility. In pregnant women, the presence of substantial niches may be linked to potentially life-threatening complications, including cesarean scar dehiscence, uterine rupture, placenta accreta spectrum disorders, placenta previa, and cesarean scar ectopic pregnancy. Given the potential dangers associated with uterine niche occurrence, numerous studies in recent years have delved into the concept of cesarean scar niche, exploring its risk factors, diagnostic approaches, and treatment options. Various diagnostic modalities, such as two- or three-dimensional transvaginal ultrasonography, two- and three-dimensional sono-hysterography, hysterosalpingography, hysteroscopy, or magnetic resonance imaging, can be employed to detect uterine niches. However, none of these diagnostic methods is universally accepted as the “gold standard,” and there remains a lack of unequivocal guidelines on certain aspects related to the diagnosis of cesarean scar niche. These niches, characterized by hypoechoic regions within the myometrium at the site of a previous CS scar, pose diagnostic complexities and provoke inquiries into their prevalence, factors influencing their development, clinical presentations, and appropriate therapeutic approaches. As CS rates rise, this review aims to understand and address uterine niches and mitigate their impact on maternal health and reproductive outcomes.